Asymmetric C-C bond formation by the mixed oxidative coupling of 1,1′-bi-2-naphthyl esters

Article abstract of DOI:10.1016/S0957-4166(02)00173-8

Asymmetric C-C bond formation was effected by the oxidative coupling of two different ester enolates using (R)-(+)-1,1′-bi(2-naphthol) as a common tether which served to link together both ester moieties in an asymmetric environment. Reduction of the corr

Full text of DOI:10.1016/S0957-4166(02)00173-8

TETRAHEDRON:
ASYMMETRY
Pergamon
Tetrahedron: Asymmetry 13 (2002) 753–757
Asymmetric CꢀC bond formation by the mixed oxidative
coupling of 1,1%-bi-2-naphthyl esters
Aurelio G. Csa´ky¨,* M. Bele´n Mula, Myriam Mba and Joaqu´ın Plumet
Departamento de Qu´ımica Orga´nica I, Facultad de Qu´ımica, Universidad Complutense, 28040 Madrid, Spain
Received 25 March 2002; accepted 9 April 2002
Abstract—Asymmetric CꢀC bond formation was effected by the oxidative coupling of two different ester enolates using
(R)-(+)-1,1%-bi(2-naphthol) as a common tether which served to link together both ester moieties in an asymmetric environment.
Reduction of the corresponding succinates afforded diastereomerically pure 2,3-disubstituted-1,4-butanediols. © 2002 Published
by Elsevier Science Ltd.
1. Introduction
of achieving a high degree of simple diastereoselectivity
(syn:anti ratio) in the newly formed CꢀC linkage. All
asymmetric variants thus far reported for this reaction
make use of chiral amides or esters as starting materials
in auxiliary controlled processes. High levels of induced
diastereoselectivity have been achieved in this fashion
for the homo-coupling of enolates, giving rise to sym-
metrical (either meso or C2) 1,4-dicarbonyl compounds.
Asymmetric CꢀC bond formation is one of the major
concerns in modern organic synthesis. Therefore, a
wide variety of procedures have been developed for this
purpose. Among them, those that make use of enolates
have been most amply used.1
The coupling of the enolates of carboxylic acid deriva-
tives constitutes a useful extension of the many syn-
thetic possibilities of the chemistry of enolates.2 This
procedure consists of enolization and subsequent oxida-
tion of the enolate to a radical cation followed by an
intermolecular coupling.3 The method allows for a new
CꢀC bond formation, affording 1,4-dicarboxylic acid
derivatives (Scheme 1).
The oxidative mixed coupling of two different enolates
would be a useful extension of this CꢀC bond forming
process. However, this reaction is not possible in an
intermolecular fashion due to competitive homo-cou-
pling of each of the starting materials, which gives rise
to mixtures of all possible homo- and mixed-coupling
products.4 We report herein the first asymmetric cou-
pling of two different ester enolates in an intramolecu-
lar fashion, to afford, after reduction, diastereo-
merically pure 2,3-disubstituted 1,4-butanediols.
One of the key features of the oxidative dimerization
reaction of carboxylic acid derivatives is the possibility
O
R1
X
X
M
X
X
O
O
R1
syn
O
M
X
M
X
R1
R1
O
O
O
X
X
[ox]
Coupling
BM
-BH
E/Z
R1
R1
R1
+
X
O
R1
M
R1
anti
O
Scheme 1.
* Corresponding author. E-mail: csaky@quim.ucm.es
0957-4166/02/$ - see front matter © 2002 Published by Elsevier Science Ltd.
PII: S0957-4166(02)00173-8

754
A. G. Csa´ky¨ et al. / Tetrahedron: Asymmetry 13 (2002) 753–757
Finally, compounds 5 were reduced (LiAlH4, 4 equiv.)
2. Results and discussion
to the optically pure 2,3-diarylbutanediols 6, with com-
plete recovery of the chiral inducer (Table 1). The
diastereomeric purity of compounds 6 was determined
from the analysis of the 19F NMR (CDCl3, 141.2 MHz)
spectra of the corresponding Mosher’s diester deriva-
tives. The (2R,3R)-absolute configuration of com-
pounds 6 was deduced by correlation of the l value
exhibited in the 19F NMR (CDCl3, 141.2 HMz) spectra
of the Mosher’s diester of (−)-(2R,3R)-2,3-diphenyl-1,4-
butanediol 6f with previously reported RX data.7
Our strategy makes use of (R)-(+)-1,1%-bi(2-naphthol)5
(Ra)-1 as a common tether in order to bring together
both ester moieties in a chiral environment. This would
allow the mixed coupling of both esters to take place in
an intramolecular asymmetric fashion6 (Scheme 2).
Therefore, (Ra)-1 was first monoesterified with car-
boxylic acids 2 (1 equiv., DCC, DMAP, CH2Cl2) to
give the monoesters 3. The free hydroxyl group of
compounds 3 was then esterified with a different car-
boxylic acid 2 (1 equiv., DCC, DMAP, CH2Cl2) to give
the diesters 4. With the diesters 4 in hand, the
intramolecular coupling reaction (TiCl4, Et3N) was car-
ried out. The results are gathered in Table 1.
3. Conclusion
In conclusion, in this work we have put forward the
scope and limitations of a new method of asymmetric
CꢀC bond formation based on the mixed coupling of
ester enolates, which allows for the formation of
The reaction took place without complications of inter-
molecular coupling, giving rise to the cyclic 1,4-diesters
5, which were obtained as single diastereomers with cis
relative stereochemistry between R1 and R2. This was
diastereomerically
butanediols.
pure
2,3-disubstituted
1,4-
1
evidenced by inspection of their H NMR (CDCl3, 200
MHz) spectra, which were compared with that of 5f
(R1, R2=Ph).7 High yields were obtained in the mixed
coupling of arylacetic esters irrespective of the electron-
donating or electron-withdrawing character of the aro-
matic moiety (entries 1–3).8,9 Yields were lower when
one of the ester counterparts was aliphatic (entry 4),
and no mixed coupling reaction was observed when
both esters were aliphatic (entries 5 and 6).10
4. Experimental
4.1. General
All starting materials were commercially available
research-grade chemicals and used without further
purification. CH2Cl2 was distilled after refluxing over
CaCl2 under Ar. Silica gel 60 F254 was used for TLC,
O
O
R2CH2CO2H
R1CH2CO2H
R1
R2
R1
O
O
OH
O
2
2
DCC, CH2Cl2
DMAP
DCC, CH2Cl2
OH
OH
DMAP
O
4
3
(Ra)-1
i) TiCl4
CH2Cl2
ii) Et3N
O
R1
R1
R2
O
O
LiAlH4
Et2O
HO
OH
R2
O
6
5
Scheme 2.
Table 1. Mixed intramolecular coupling of binaphthyl esters 4
No.
4
R1
R2
5 (%)a
6 (%)a
1
2
3
4
5
4a
4b
4c
4d
4e
Ph
Ph
p-MeO–C6H4
p-CF3–C6H4
p-CF3–C6H4
Et
(Ra,2R,3R)-5a (85)
(Ra,2R,3R)-5b (85)
(Ra,2R,3R)-5c (85)
(Ra,2R,3S)-5d (70)b
5e (−)
(2R,3R)-6a (70)
(2R,3R)-6b (70)
(2R,3R)-6c (70)
(2R,3R)-6d (60)
6e (−)
p-MeO–C6H4
Ph
Et
Pr
a Isolated yields.
b The change in absolute stereochemistry corresponds with a change in the CIP-nomenclature rules.

A. G. Csa´ky¨ et al. / Tetrahedron: Asymmetry 13 (2002) 753–757
755
and the spots were detected with UV or vanillin solu-
tion. Flash column chromatography was carried out on
silica gel 60. IR spectra have been recorded as CHCl3
react at 25°C for 3–5 h. Addition of Et2O, filtration and
evaporation of the solvent under reduced pressure
yielded an oil which was purified by flash chromatogra-
phy (hexane/diethyl ether 5:1).
1
solutions. H, 13C and 19F NMR spectra were recorded
at 200, 50.5 and 141.2 MHz, respectively in CDCl3
solution. MS spectra were carried out by EI at 70 eV.
4.3.1. Data for (Ra)-(4-methoxyphenyl)acetic acid 2%-
phenylacetoxy-[1,1%]binaphthalenyl-2-yl ester 4a. White
solid (95% yield), mp=93–95°C (hexane–AcOEt). IR
4.2. General procedure for the synthesis of (Ra)-1,1%-bi-
2-naphthol monoesters of alkyl and aryl acids 3
1
(CHCl3) w 3064, 3029, 1753, 1748, 1235 cm−1. H NMR
(200 MHz, CDCl3) l 3.23 (s, 2H), 3.29 (2, 2H), 3.65 (s,
3H), 6.40–8.00 (m, 21H) ppm. 13C NMR (25.5 MHz,
CDCl3) l 40.0, 40.8, 55.1, 121.8, 123.4, 125.6, 126.0,
126.7, 126.8, 127.9, 128.2, 129.1, 129.4, 130.0, 133.5,
133.3, 146.8, 158.3, 169.7, 170.0 ppm. Anal. calcd for
C37H28O5: C, 80.42; H, 5.11. Found C, 80.59; H 5.36%.
A solution of DCC (1.1 mmol) and DMAP (0.06
mmol) in CH2Cl2 (4 mL) was added dropwise to a
solution of (Ra)-(+)-1,1%-bi-2-naphthol (1.0 mmol) and
the carboxylic acid (1.0 mmol) in CH2Cl2 (4 mL) at
0°C. The mixture was allowed to react at 25°C for 3–5
h. Addition of Et2O, filtration of the precipitate formed
and evaporation of the solvent under reduced pressure
yielded an oil which was purified by flash chromatogra-
phy (hexane/diethyl ether 5:1).
4.3.2. Data for (Ra)-phenylacetic acid 2%-[2-(4-trifluoro-
methyl-phenyl)acetoxy]-[1,1%]bi-naphthalenyl-2-yl
ester
4b. White solid (90% yield), mp=108–110°C (hexane–
AcOEt). IR (CHCl3) w 3055, 3036, 1755, 1739, 1241
4.2.1. Data for (Ra)-phenylacetic acid 2%-hydroxy-
[1,1]binaphthalenyl-2-ester 3a. White solid (95% yield),
mp=60–62°C (hexane–AcOEt). IR (CHCl3): w 3600–
3500, 3065, 3034, 1750, 1240 cm−1. 1H NMR (200
MHz, CDCl3): l 3.35 (s, 2H), 6.40–8.00 (m, 17H) ppm.
13C NMR (50 MHz, CDCl3) l 40.8, 113.8, 118.2, 121.6,
123.1, 123.5, 124.5, 125.7, 126.3, 126.9, 127.4, 127.9,
128.2, 128.3, 128.8, 129.0, 130.4, 130.7, 132.3, 132.5,
133.5, 148.0, 151.7, 170.8 ppm. Anal. calcd for
C28H20O3: C, 83.15; H, 4.98. Found: C, 83.01; H,
5.23%.
1
cm−1. H NMR (200 MHz, CDCl3) l 3.32 (s, 2H), 3.38
(s, 2H), 6.60–8.00 (m, 21H) ppm. 13C NMR (50 MHz,
2
CDCl3) l 41.0, 41.1, 115.4 (q, JCF=196 Hz), 121.6,
121.7, 125.3, 125.9, 126.1, 126.8, 127.0, 128.1, 128.4,
129.2, 129.4, 129.6, 129.7, 148.5, 167.9, 168.5 ppm.
Anal. calcd for C37H25F3O4: C, 75.25; H 4.27. Found:
C, 75.43; H 4.48%.
4.3.3. Data for (Ra)-(4-methoxyphenyl)acetic acid 2%-[2-
(4-trifluoromethylphenyl)acetoxy]-[1,1%]binaphthalenyl-2-
yl ester 4c. White solid (90% yield), mp=104–106°C
(hexane–AcOEt). IR (CHCl3) w 3053, 3025, 1758, 1753,
4.2.2. Data for (Ra)-(4-methoxyphenyl)acetic acid 2%-
hydroxy-[1,1]binaphthalenyl-2-yl ester 3b. White solid
(95% yield), mp=55–57°C (hexane–AcOEt). IR
1
1240 cm−1. H NMR (200 MHz, CDCl3) l 3.25 (s, 2H),
3.37 (s, 2H), 3.67 (s, 3H) 6.40–8.00 (m, 20H) ppm. 13C
NMR (25.5 MHz, CDCl3) l 40.0, 40.8, 55.1, 113.7,
115.5 (q, 2JCF=196 Hz), 121.5, 123.1, 123.4, 125.4,
125.9, 126.8, 128.0, 129.2, 129.4, 130.0, 131.4, 131.6,
133.1, 133.2, 136.7, 146.7, 158.4, 168.8, 170.1 ppm.
Anal. calcd for C38H27F3O5: C, 73.54; H, 4.39. Found
C, 73.19; H, 4.47%.
1
(CHCl3) w 3600–3500, 3063, 3038, 1758, 1235 cm−1. H
NMR (200 MHz, CDCl3): l 3.37 (s, 2H), 3.68 (s, 3H),
5.25 (bs, 1H), 6.40–8.00 (m, 16H) ppm. 13C NMR (50
MHz, CDCl3) l 40.1, 55.2, 113.9, 117.9, 121.7, 123.3,
124.3, 124.7, 125.7, 126.8, 128.0, 129.1, 129.8 131.4,
133.5, 148.1, 151.7, 158.5, 171.2 ppm. Anal. calcd for
C29H22O4: C, 80.17; H, 5.10. Found: C, 79.95; H,
5.12%.
4.3.4. Data for (Ra)-propionic acid 2%-[2-(4-
methoxyphenyl)acetoxy]-[1,1%]binaphthalenyl-2-yl ester
4d. Colorless oil (90% yield). IR (CHCl3) w 3056, 3033,
1757, 1735, 1243, 1213 cm−1. 1H NMR (200 MHz,
CDCl3) l 0.63 (t, J=7.5 Hz, 3H), 1.97 (q, J=7.5 Hz,
2H), 3.25 (s, 2H), 3.67 (s, 3H), 6.40–6.70 (m, 4H),
7.10–7.45 (m, 8 H), 7.75–8.02 (m, 4H) ppm. 13C NMR
(25.5 MHz, CDCl3) l 8.7, 27.5, 40.1, 55.2, 113.7, 121.8,
123.4, 123.6, 125.1, 125.6, 126.1, 126.7, 128.0, 129.4,
130.1, 133.4, 146.8, 158.4, 170.1, 172.8 ppm. Anal. calcd
for C32H26O5: C, 78.35; H, 5.34. Found: C, 78.13; H,
5.13%.
4.2.3. Data for (Ra)-propionic acid 2%-hydroxy-
[1,1]binaphthalenyl-2-yl ester 3c. Colorless oil (90%
yield). IR (CHCl3) w 3600–3500, 3065, 3030, 2985, 1736,
1224 cm−1. 1H NMR (200 MHz, CDCl3) l 0.55 (t,
J=7.2 Hz, 3H), 1.95 (q, J=7.2 Hz, 1H), 2.03, (q,
J=7.2 Hz, 1H) 6.90–8.00 (m, 12H) ppm. 13C NMR (50
MHz, CDCl3) l 8.9, 27.5, 114.2, 118.4, 121.9, 123.6,
124.7, 125.8, 126.8, 128.4, 148.2, 151.9, 174.0 ppm.
Anal. calcd for C23H18O3: C, 80.68; H, 5.30. Found: C,
80.41; H, 5.47%.
4.3. General procedure for the synthesis of (Ra)-1,1%-bi-
4.3.5. Data for (Ra)-butyric acid 2%-propionyloxy-
[1,1%]binaphthalenyl-2-yl ester 4e. Colorless oil (90%
yield). IR (CHCl3) w 3058. 3031, 2985, 1736, 1218 cm−1.
1H NMR (200 MHz, CDCl3) l 0.48 (t, J=7.4 Hz, 3H),
0.61 (t, J=7.6 Hz, 3H), 1.03–1.30 (m, 2H), 1.95–2.20
(m, 4H), 7.10–8.00 (m, 12H) ppm. 13C NMR (25.5
MHz, CDCl3) l 8.7, 11.4, 17.9, 27.5, 35.7, 118.2, 121.9,
123.5, 125.6, 126.7, 127.9, 129.3, 133.5, 146.7, 171.8,
2-naphthol diesters of alkyl and aryl acids 4
A solution of DCC (1.1 mmol) and DMAP (0.06
mmol) in CH2Cl2 (4 mL) was added dropwise to a
solution of the corresponding (Ra)-(+)-1,1%-bi-2-naph-
thol monoester 3 and the carboxylic acid (1.0 mmol) in
CH2Cl2 (4 mL) at 0°C. The mixture was allowed to

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A. G. Csa´ky¨ et al. / Tetrahedron: Asymmetry 13 (2002) 753–757
172.6 ppm. Anal. calcd for C27H24O4: C, 78.62; H, 5.86.
Found: C, 78.64; H, 5.69%.
4.4.4. Data for (−)-(Ra,2R,3S)-2-(4-methoxyphenyl)-3-
methylsuccinic acid [1,1%]binaph-thalenyl-2,2%-diol ester
5d. Colorless oil (70% yield). [h]2D5=−45.7 (c 0.7,
CHCl3). IR (CHCl3) w 3060, 3034, 2985, 1774, 1748,
1230 cm−1. 1H NMR (200 MHz, CDCl3) l 0.89 (d,
J=6.6 Hz, 3H), 3.22 (m, 1H) 3.70 (s, 3H), 3.80 (s, 1H),
6.80–8.00 (m, 16H) ppm. 13C NMR (25.5 MHz, CDCl3)
l 8.9, 27.5, 46.2, 54.3, 114.6, 121.0, 121.9, 125.9, 126.7,
127.1, 128.1, 128.6, 130.3, 131.7, 133.3, 133.552, 147.9,
159.8, 170.7, 172.2 ppm. Anal. calcd for C32H24O5: C,
78.67; H, 4.95. Found: C, 78.85; H, 4.71%.
4.4. General procedure for the intramolecular oxidative
coupling of diesters 4
A solution of the diester 4 (0.8 mmol) in dry CH2Cl2 (4
mL) was cooled down under argon at −45°C and TiCl4
(3.2 mmol, 1.0 M solution in CH2Cl2) was added
slowly. The mixture was stirred at −45°C for 30 min
and Et3N (3.2 mmol) was added dropwise. The red
solution turned blue–violet, and was allowed to react
for a further 3 h at –45°C. The mixture was quenched
with HCl (0.5N) and the aqueous layer was extracted
twice with CH2Cl2. The organic layers were combined
and dried over magnesium sulfate. Evaporation of the
solvent under reduced pressure yielded an orange solid,
which was purified by flash chromatography (hexane/
ether 10:1).
4.5. General procedure for the reduction of diesters 5
into butanediols 6
A solution of diester 5 (0.5 mmol) in dry THF (5 mL)
was added dropwise to a suspension of LiAlH4 (8.0
mmol) in dry THF (3 mL). The mixture was allowed to
react at rt until the reaction was completed (3–5 h,
following the reaction by TLC). Ethyl acetate (3 mL),
wet diethyl ether (3 mL), water (3 mL) and 0.5N HCl (3
mL) were added in that order to quench excess LiAlH4.
The organic layer was separated and the aqueous one
was extracted twice with diethyl ether. All the organic
layers were combined and dried over MgSO4. Filtration
and evaporation of the solvent gave rise to a colorless
oil which was purified by flash chromatography
(CH2Cl2/MeOH 20:1) to give two fractions: the first
one was a white solid which was characterized as
(Ra)-(+)1,1%-bi-2-naphthol, and the second one was a
colorless oil which was characterized as the correspond-
ing compound 6.
4.4.1. Data for (−)-(Ra,2R,3R)-2-(4-methoxyphenyl)-3-
phenylsuccinic acid [1,1%]binaphtha-lenyl-2,2%-diol ester
5a. White solid (85% yield), mp=145–147°C (hexane–
AcOEt). [h]2D5=−78.9 (c 0.5, CHCl3). IR (CHCl3) w
3064, 3034, 1774, 1224 cm−1. 1H NMR (200 MHz,
CDCl3) l 3.60 (s, 3H), 4.36 (s, 2H), 6.50–8.00 (m, 21H)
ppm. 13C NMR (25.5 MHz, CDCl3) l 55.3, 56.4, 56.7,
114.3, 121.3, 122.0, 125.4, 126.0, 127.3, 128.3, 128.5,
129.9, 130.4, 131.9, 133.7, 133.8, 148.2, 159.5, 169.8
ppm. MS (m/z, %) 550 (41), 237 (100), 209 (64). Anal.
calcd for C37H26O5: C, 80.71; H, 4.76. Found: C, 80.52;
H, 4.81%.
4.5.1. Data for (−)-(2R,3R)-(4-methoxyphenyl)-3-phenyl-
1,4-butanediol 6a. Colorless oil (70% yield). [h]2D5=−37.2
1
4.4.2. Data for (−)-(Ra,2R,3R)-2-(4-trifluoromethyl-
phenyl)-3-phenylsuccinic acid [1,1%]binaph-thalenyl-2,2%-
diol ester 5b. White solid (85% yield), mp=163–165°C
(hexane–AcOEt). [h]2D5=−88.2 (c 0.5, CHCl3). IR
(c 0.8, CHCl3). IR (CHCl3) w 3300, 3065, 1603 cm−1. H
NMR (200 MHz, CDCl3) l 2.12 (bs, 2H), 3.15 (m, 2H),
3.64 (s, 3H), 3.84 (m, 4H), 6.55–7.18 (m, 9H) ppm. 13C
NMR (25.5 MHz, CDCl3) l 50.0, 51.0, 55.3, 65.6, 65.7,
113.7, 126.6, 128.3, 128.7, 131.5, 132.5, 140.7, 158.3
ppm. Anal. calcd for C17H20O3: C, 74.97; H, 7.40.
Found: C, 74.83; H, 7.23%.
1
(CHCl3) w 3056, 3035, 1778, 1232 cm−1. H NMR (200
MHz, CDCl3) l 4.35 (B part of AB system, J=11.4 Hz,
1H), 4.41 (A part of AB system, J=11.4 Hz, 1H),
6.80–8.00 (m, 21H) ppm. 13C NMR (25.5 MHz, CDCl3)
l 56.3, 56.7, 65.8, 120.7, 121.9, 125.9, 126.7, 127.1,
128.1, 128.6, 130.3, 131.7, 133.3, 133.5, 137.6, 147.9,
168.9, 169.1 ppm. MS (m/z, %) 588 (95), 286 (92), 268
(32), 247 (100). Anal. calcd for C37H23F3O4: C, 75.50;
H, 3.94. Found: C, 73.62; H, 3.71%.
4.5.2. Data for (−)-(2R,3R)-2-phenyl-3-(4-trifluoro-
methylphenyl)-1,4-butanediol 6b. Colorless oil (70%
yield). [h]2D5=−38.0 (c 0.8, CHCl3). IR (CHCl3) w 3295,
1
3060, 1600 cm−1. H NMR (200 MHz, CDCl3) l 2.07
(bs, 2H), 3.23 (m, 2H), 3.90 (m, 4H), 6.85–7.15 (m, 9H)
ppm. 13C NMR (25.5 MHz, CDCl3) l 50.8, 51.0, 65.4,
65.7, 115.5 (q, 2JCF=196 Hz), 125.1, 125.2, 126.9,
128.5, 129.1, 131.5, 140.3, 145.4 ppm. Anal. calcd for
C17H17F3O2: C, 65.80; H, 5.52. Found: C, 66.01; H,
5.74%.
4.4.3. Data for (−)-(Ra,2R,3R)-2-(4-methoxyphenyl)-3-
(4-trifluoromethylphenyl)succinic acid [1,1%]binaphthal-
enyl-2,2%-diol ester 5c. White solid (85% yield), mp=
170–172°C (hexane–AcOEt). [h]2D5=−78.1 (c 0.5,
1
CHCl3). IR (CHCl3) w 3053, 3034, 1776, 1224 cm−1. H
4.5.3. Data for (−)-(2R,3R)-2-(4-methoxyphenyl)-3-(4-
trifluoromethylphenyl)-1,4-butanediol 6c. Colorless oil
(70% yield). [h]2D5=−35.5 (c 0.7, CHCl3). IR (CHCl3) w
NMR (200 MHz, CDCl3) l 3.68 (s, 3H), 4.38 (B part of
AB system, J=11.3 Hz, 1H), 4.50 (A part of AB
system, J=11.3 Hz, 1H), 6.50–8.00 (m, 20H) ppm. 13C
NMR (25.5 MHz, CDCl3) l 55.1, 55.9, 56.3, 114.3,
115.5 (q, 2JCF=196 Hz), 120.7, 121.0, 124.6, 125.6,
126.0, 127.2, 128.3, 129.0, 129.7, 130.4, 131.7, 133.5,
147.9, 159.5, 169.6 ppm. MS (m/z, %) 618 (40), 305
(100), 277 (68). Anal. calcd for C38H25F3O5: C, 73.78;
H, 4.07. Found: C, 73.57; H, 4.21%.
1
3302, 3057, 1604 cm−1. H NMR (200 MHz, CDCl3) l
2.14 (bs, 2H), 3.19 (m, 2H), 3.65 (s, 3H), 3.90 (m, 4H),
6.55–7.30 (m, 8H) ppm. 13C NMR (25.5 MHz, CDCl3)
2
l 49.7, 51.0, 55.3, 65.3, 65.7, 113.9, 115.5 (q, JCF=196
Hz), 125.1, 125.2, 129.1, 129.5, 132.0, 144.3, 158.4 ppm.
Anal. calcd for C18H19F3O3: C, 63.52; H, 5.63. Found:
C, 63.75; H, 5.85%.

A. G. Csa´ky¨ et al. / Tetrahedron: Asymmetry 13 (2002) 753–757
757
4.5.4. Data for (−)-(2R,3R)-2-(4-methoxyphenyl)-3-
methyl-1,4-butanediol 6d. Colorless oil (60% yield).
[h]2D5=−28.5 (c 0.7, CHCl3). IR (CHCl3) w 3295, 3055,
1599 cm−1. 1H NMR (200 MHz, CDCl3) l 0.65 (d,
J=7.2 Hz, 3H), 1.95 (m, 1H), 2.65 (m, 1H), 2.70 (bs,
2H), 3.48 (dd, J=10.6, 6.4 Hz, 1H), 3.62 (dd, J=10.6,
4.4 Hz, 1H), 3.71 (s, 3H), 3.79 (dd, J=6.3, 1.1 Hz, 2H),
6.85–7.15 (m, 4H) ppm. 13C NMR (25.5 MHz, CDCl3)
l 19.3, 39.5, 50.8, 55.0, 65.4, 65.7, 113.1, 129.2, 152.6,
158.2 ppm. Anal. calcd for C12H18O3: C, 68.54; H, 8.63.
Found: C, 68.71; H, 8.74%.
4.6.5. Data for Mosher’s diester of dl-(2R*,3R*)-6f. 19F
NMR (141.2 MHz, CDCl3): l −71.85, −71.87 ppm
4.6.6. Data for Mosher’s diester of (−)-(2R,3R)-6f. 19F
NMR (141.2 MHz, CDCl3): l −71.87 ppm
Acknowledgements
Ministerio de Ciencia y Tecnolog´ıa (Project BQU2000-
0653) and REPSOL-YPF are gratefully thanked for
financial support.
4.6. General procedure for the synthesis of Mosher’s
diesters of compounds 6
References
(+)-(S)-a-Methoxy-h-trifluoromethylphenylacetyl chlo-
ride (1.25 equiv.), Et3N (1.25 equiv.) and DMAP (0.015
equiv.) were added to a solution of 6 (0.02 mmol) in
anhydrous CH2Cl2 (1 mL), and the solution was stirred
for 12 h at 20°C. After washing with saturated
NaHCO3 (2×1 mL) and 5% HCl (2×1 mL), the organic
phase was dried (MgSO4) and evaporated to afford a
pale yellow oil.
1. Stereoselective Synthesis, Houben-Weyl, Helmchen, G.;
Hoffmann, R. W.; Mulzer, J. U.; Schaumann, E., Eds.;
Thieme: Stuttgart, 1996, Vol. E21/3.
2. Csa´ky¨, A. G.; Plumet, J. Chem. Soc. Rev. 2001, 30, 313.
3. For an example of intramolecular asymmetric coupling,
see: Studer, A.; Hintermann, T.; Seebach, D. Helv. Chim.
Acta 1995, 78, 1185.
4. Langer, T.; Illich, M.; Helmchen, G. Synlett 1996, 1137.
5. For the use of binaphthyl esters in the oxidative homo-
coupling of phenylacetic acid, see: Rao, V. D.; Periasamy,
M. Tetrahedron: Asymmetry. 2000, 11, 1151.
4.6.1. Data for Mosher’s diester of (−)-(2R,3R)-6a. 19F
NMR (141.2 MHz, CDCl3): l −71.86, −71.89 ppm.
6. Schmittel, M.; Burghart, A.; Maklisch, W.; Reising, J.;
4.6.2. Data for Mosher’s diester of (−)-(2R,3R)-6b. 19F
NMR (141.2 MHz, CDCl3): l −63.03, −71.78, −71.87
ppm.
So¨llner, R. J. Org. Chem. 1998, 63, 396.
7. The stereochemistry of the product of the oxidative
homo-coupling of 5e has been previously reported by
X-ray analysis. See Ref. 5.
8. (a) Kise, N.; Kumada, K.; Terao, Y.; Ueda, N. Tetra-
hedron 1998, 54, 2697; (b) Kise, N.; Ueda, T.; Kumada,
K.; Terao, Y.; Ueda, N. J. Org. Chem. 2000, 65, 464.
9. It is worth mentioning that p-CF3 substitution inhibited
the intramolecular coupling of arylacetyloxazolidinones.
See Ref. 8.
4.6.3. Data for Mosher’s diester of (−)-(2R,3R)-6c. 19F
NMR (141.2 MHz, CDCl3): l −62.99, −71.72, −71.80
ppm
4.6.4. Data for Mosher’s diester of (−)-(2R,3R)-6d. 19F
NMR (141.2 MHz, CDCl3): l −71.77, −72.06 ppm
10. A mixture of products was obtained in this case